Apparatus for automatically distributing the air blast to blast furnaces



THE A Filed April 5, 1956 BLAST BLAST FURNACES 2 Sheets-Sheet 1 May 12, 1959' F. E. DEMMON 2,836,307

' APPARATUS FOR AUTO ICALLY DISTRIBUTING INVENTOR. FLOYD E DEM/VON,

/2/'s Attorney.

May 12, 1959 F. E. DEMMON 2,886,307

I APPARATUS FOR AUTOMATICALLY DISTRIBUTING THE AIR BLAST TO BLAsT FURNACES Filed April s, 1956 2 Sheets-Sheet 2 l l l l I 42 A uvvgvroe: 428 I FLOYD E. DEMMO/V,

+7'0 controllers 50 for other Iuyeres A his Al/omey.

United States Patent Floyd E. Demmon, Hobart, Ind., assignor to United States Steel Corporation, a corporation of New Jersey Application April 3, 1956, Serial No. 575,802

18 Claims. (Cl. 266-30) This invention relates to apparatus for automatically distributing the air blast to blast furnaces. The air is delivered to the furnace through a plurality of tuyeres arranged around the periphery of the furnace. The con trol of the air to the furnace is important in obtaining best operating conditions and controls for that purpose are disclosed in the patents to Hayes No. 1,726,298, dated August 27, 1929, and Burke No. 2,083,046, dated June 8, 1937. While the controls shown therein will operate satisfactorily under normal conditions, they will not operate satisfactorily when unusual conditions occur in the furnace. In actual blast furnace operation it is common for unusual conditions to occur. In some instances the pressure of the air will decrease to a point where operation of the furnace may become dangerous, in other instances conditions within the blast furnace change rapidly and the control will tend to hunt or cycle. Occasionally it is necessary to back-draft the furnace and special means are required to prevent dangerousoperation of the control at'this time. The blastpressure may become exceedingly high and functioning of the control must be discontinued to prevent damage.

It is therefore an object of my invention to provide a control for automatically distributing air blast to blast furnaces in which means are provided for changing the operation of the control during unusual conditions.

Another object is to provide such a control which will operate without excessive hunting.

These and other objects will be more apparent after referring to the following specification and attached drawings, in which:

Figure l is a schematic view of a blast furnace showing the arrangement of the tuyeres; and

Figure 2 is a schematic view of the control of my invention.

Referring more particularly to the drawings, the reference numeral 2 indicates the conduit for supplying air to the tuyeres T of the blast furnace F. The conduit 2 terminates in a bustle pipe 4 from which separate pipe lines 6 lead to the individual tuyeres T. Located in each of the pipe lines 6 is a plug valve 10 and venturi 12. The position of the plug valve 10 is controlled by means of an hydraulic cylinder 14. A piston rod 16 connects the piston of the hydraulic cylinder 14 to the stern of the valve 10. A cable 18 is connected to the piston rod 16 and passes over a rotatable sheave 20 with its free end being connected to counterweight 22. The cable 18 is attached to the sheave 20 so that it moves therewith. A cam 24 is connected to shaft 26 which supports the sheave 20. A cam follower 28 is in contact with cam 24. The cam follower 28 is connected by means of a rod 30 to an Askania Pilot relay 32. This well known device, by means of a diaphragm and hydraulic pilot valve, produces a hydraulic pressure proportional to the movement of rod 30 which is emitted through oil delivery line 38. The oil delivery line 38 is connected to pressure switches 40 and 42. Switch 40 has a normally closed contact 40c and switch 42 a normally open contact 420. It will be "ice seen that the position of valve 10 is indicated by the position of sheave 20 and that the position of rod 30 is dependent upon the position of the sheave 20 so that the pressure supplied through line 38 will vary according to the position of the plug valve 10.

Pressure lines 44 and 46 are connected to the high and low pressure sides of venturi 12, respectively. Lines 44 and 46 lead to opposite sides of a diaphragm 48 forming part of a well known Askania regulator or controller 50. A second diaphragm 52 is connected to the high pressure side of an orifice plate 54 through line 56. A pivotally mounted oil jet 58 is located between diaphragms 48 and 52 and is mechanically connected thereto for movement therewith. Oil is supplied to jet 58 from oil tank 60 through conduit 62 and oil from the control is returned to the tank 60 through line 64. Oil from jet 58 is supplied through a delivery block and two orifices to lines 66 and 68. A shut-off valve 70 is arranged in the lines 66 and 68 and is operated by means of solenoid 72. An oil line 74 is connected to oil supply line 62 between the jet 58 and tank 60. A three-way valve 76 is provided in the line 74 to control flow of oil to lines 66 and 68. Operation of valve 76 is controlled by solenoids 78 and 80 Energization of solenoid 78 causes the valve 76 to move to the position where oil flows to line 68 and energization of solenoid 80 causes the valve 76 to move to the position where oil will flow to the line 66. Lines 66 and 68 are connected to opposite sides of the piston of cylinder 14. When oil flows through line 66, valve 10 will move toward its closed position and when oil flows through line 68 valve 10 will move toward its open position. Suitable shut-oil valves may be provided in the various oil lines as shown. Associated with the Askania regulator 50 is a limit switch 82 which includes a cam 84, cam follower 86 and contacts 82c and 8201. The parts so far described are all part of the Askania regulator. It will be understood that a regulator 50 and associated parts are provided for each of the tuyeres.

Manually operated switch 88 having contacts 88a, 88b and 880 is connected to control the energization of solenoids 72, 78 and 80. Only one switch 88 is necessary to control the operation of the solenoids of all of the regulators 50. The orifice 54 is located in a tap line 90 connected to conduit 2. A motor operated burden valve 92 is located in the line 90 between the orifice 54 and con duit 2. A by-pass 94 may be provided around the valve 92 with the necessary valves being provided as shown. The line 56 is connected to the diaphragm 52 of each of the regulators 50. Motor 96 controls the position of valve 92. Power for operating burden motor 96 is supplied from power lines L3 and L4 through a switch 98 forming part of controller motor timer 100. Switch 98 is actuated by motor 102 to interrupt flow of current to motor 96 a certain number of seconds per minute, depending upon the setting of the timer. Therefore, the operation of motor 96 will be intermittent. Associated with motor 96 is a speed control knob- 104, the position of which is adjusted by means of a speed control motor 106. Motor 106 is reversible and will operate in either direction depending upon the pressure in bustle pipe 4. The operation of motor 106 is controlled by means of a control 108 having a pressure responsive element 109 communicating with the bustle pipe 4 or hot blast main 2. Assuming that the control 108 is set for 17.3 pounds per square inch gage, current will not flow through the control 108 as long as the pressure is below 17.3 pounds per square inch gage and relay coil 110 will remain deenergized with the directional circuit to the speed control motor 106 being completed in the direction which adjusts the speed control knob 104 to the slow position as shown. When the pressure increases beyond- 17.3 pounds per square inch gage, control 108 will operate to complete a circuit through relay coil 110, thus causing its contactor 1100 to move to its upper position which completes the directional circuit for adjusting the speed control knob 104 to the fast position. Contact 1120 operated by relay coil 112 is in series with controller 108. Relay coil 112 is connected to power line L2 through line 114, and to line L1 through line 116, constant 420, contact 820, and line 118. A low pressure responsive switch 120 is controlled by means of a pressure element 122 communicating with the bustle pipe 4. Contact 1200 of switch 120 is located in the neutral line of the directional circuit of motor 96. If the switch 120 is set so that it will open when the pressure in the bustle pipe drops below 13 pounds per square inch gage the motor 96 will stop when the pressure is below 13 pounds per square inch gage. Contact 1220 operated by relay coil 122 is provided in the directional circuit to operate the motor 96 in the direction to close the valve 92. Contact 1240 operated by relay coil 124 is provided in the directional circuit. When coil 124 is energized contact 1240 will open preventing motor 96 from opening the valve 92. Relay coil 124 also operates contact 12401 which can complete a circuit through coil 122. Over pressure control 126 has a pressure responsive element 128 communicating with the bustle pipe 4. When the pressure reaches a predetermined high pressure current will flow from line L2 through control 126, line 128 and through relay coils 130 and 132 connected in parallel to line L1. Energization of coil 130 will close its contacts 1300 and 13001 to complete a circuit to lines L1 and L2 through solenoids 72 and 78. Energization ol coil 132 will close its contact 1320 to complete a circuit through alarm bells 134. Tap line 136 is taken from line 68 to pressure switch 138 having normally open contact 1380. Tap line 140 is taken from line 66 to pressure switch 142 having normally open contact 1420 and normally closed contact 14201. Closing of contact 1380 will complete a circuit through light 144 and closing of contact 1420 will complete a circuit through light 146. Horn 148 is connected to lines L1 and L2 through contact 1500 which is controlled by relay coil 150'.

The operation of the control is as follows:

It is placed on automatic by turning the limit switches 82 and back draft switch 88 on automatic. In the drawings the limit switch 82 is shown on automatic and the back draft switch on manual. The contacts 88a, 88b and 880 will be open when the switch 88 is on automatic. Each pressure switch 40 is set so its contacts 400 will remain closed as long as its associated plug valve is open at least 50% and each switch 42 is set so its contacts will remain open until its associated plug valve is more than 80% of full open. For various reasons it is not desirable that the plug valves open full wide nor close full shut but the range set forth above may vary. The control 108 is set so that its contacts will close when the pressure in the bustle pipe reaches 17.3 pounds per square inch gage. The low pressure responsive switch 120 is set so that it will open when the pressure in the bustle pipe drops below 13 pounds per square inch gage. Control 126 is set so that its contacts will close when the pressure in the bustle pipe reaches 19 pounds per square inch gage. These pressures are all relative and they may be varied according to the particular furnace on which the control is installed. However, the control 108 is always set at a relatively high pressure above which it is not desired to operate and the control 126 is set at a pressure slightly above that of control 108. Pressure responsive switch 120 is set at a pressure below which it is not desired to operate in a normal manner. During normal operation the plug valves are open an amount which permits equal amounts of air to flow to each tuyere. The flow of air to each tuyereis measured by the difference of pressure in lines 44 and 46. This pressure differential is balanced in the associated regulator 50 against the master reference impulse received through line 56. If the air flow to one of the tuyeres decreases, the differential pressure will also decrease. This causes jet 58 to move to the left thus causing oil to flow through pipe 68 to open the associated plug valves 10 until the pressure difierential 4446 again equals the pressure dififerential in the lines to the other tuyeres. Of course, the pressure differential of the other tuyeres may also vary, but eventually they will return to the point where the pressure differential in the lines to all of the tuyeres is equal.

When there is an obstruction in one of the tuyeres the flow of air to that tuyere will decrease and the associated plug valve will open. If the obstruction is not eliminated the plug valve will continue to open to more than thus closing contacts 420 associated with that tuyere. This completes a circuit from line L1 through contact 820, contact 420, lead 116, contact 12401 and relay coil 122 to line L2. Energization of relay coil 122 closes its contact 1220 causing the burden motor 96 to operate in a direction to partially close the burden valve 92. Upon closing of contacts 420 a circuit is also completed to relay 112 from line L1 through line 118, contacts 820, contacts 420 and line 116 to line L2, thus energizing coil 112 and opening contacts 1120 thereby preventing the energization of relay coil and the moving of contacts 1100 to the upper position. This is to insure that speed control knob 104 will not be moved to the fast position when the directional circuit of burden motor 96 is completed to partially close burden valve 92. This closing of the burden valve 92 will disturb the balance between diaphragms 48 and 52 of each of the regulators 50 except the one for the obstructed tuyere in such a manner that the jet 58 will move to the right thus causing oil to flow through conduit 66 to partially close all of the valves 10 except the one leading to the obstructed tuyere. As said valves close, more air in the bustle pipe is diverted to the obstructed tuyere until the obstruction is burned or blown away. If the obstruction is not burned or blown away the valves 10 will continue closing and the blast pressure will rise. Eventually all contacts 400 will be open except that associated with the obstructed tuyere. Most of the air will then flow to the obstructed tuyere and will burn or blow the obstruction away. When this occurs the flow of air to that tuyere increases and the associated difierential pressure 4446 will cause the jet 58 of the associated control 50 to move to the right and direct oil to conduit 66 to close the associated valve 10 to the same position as all the other plug valves. When this last plug valve closes below 50% contacts 400 associated therewith will open. This opens the last of the parallel circuits to relay coil 124, thus causing its contacts 1240 to close and contacts 12401 to open. Closing of contact 1240 will complete the directional circuit of motor 96 in such a direction as to open burden valve 92. This increases the pressure in conduit 56 thus moving all the jets 58 to the left and causing all the plug valves 10 to open to a position within the control range. When the first plug valve 10 reaches the control range contact 400 associated therewith will close completing a circuit through relay coil 124 thus stopping operation of the burden motor 96. In this manner the control returns to its normal operating condition and distributes the air equally among the tuyeres.

When one of the plug valves 10 opens completely pressure will build up in the conduit 68 associated therewith, thus closing the associated contacts 1380. This completes a circuit from line L1 to line L2 through green light 144, thus warning the operator that the associated valve 10 is all the way open. When one of the plug valves is all the way closed pressure will build up in associated line 66 thus causing associated contacts 1420 to close and 14201 to open. Closing of contact 1420 completes the circuit through red light 146, thus warning the operator that that particular plug valve is all the way closed. Each of the contacts 14201 is in series with relay coil and the contacts 14201 associated with one v alve are in parallel with the contacts 142c1 associated with the other valves. Thus relay coil 150 will be energized as long as any one of the plug valves is open. However, when all of the valves are closed all of the contacts 142c1 will be open and relay coil 150 will be deenergized, thus closing its contacts 1500 and completing a circuit through horn 148, giving an audible signal to the operator.

When there is an excessively high pressure in the bustle pipe 4 it is advantageous to have the burden motor 96 operate at a high speed to relieve the high pressure quickly. For best operation the burden motor 96 should operate to open rapidly to relieve the high pressure but should operate slowly to close the burden valve with cycling conditions being checked by the interrupter 100. When the pressure in the bustle pipe exceeds 17.3 pounds per square inch the contacts of control 108 will close, thus completing a circuit through relay coil 110 and causing contact 110c to move to its upper position completing the directional circuit to motor 106 whichoperates to adjust the speed control knob 104 to the fast position so that the operation of the burden motor 96 will open rapidly.

In some instances there is a high pressure condition in the bustle pipe 4 which calls for rapid operation of the burden motor 96 to open the burden valve 92 while at the same time there is an obstructed tuyere which causes the associated plug valve to open and all the other plug valves to close. Thus the burden valve 92 will close rapidly and aggravate the high pressure condition. Since it is more important to relieve the high pressure in the bustle pipe the control 126 is provided. When the pressure in the bustle pipe increases to 19 pounds per square inch the contacts of control 126 close, thuscompleting circuits through relay coils 130 and 132. Energization of relay coil 130 closes its contacts 130a and 130c1. Closing of contacts 130:: completes circuits from line L1 through contact 130a and each solenoid 7 8 to line L2. Closing of contacts 130c1 completes circuits from line L1 through contact 13001 and each solenoid 72 to line L2. Energization of solenoids 72 closes valves 70, thus preventing the controls 50 from operating automatically. Energization of solenoids 78 causes valves 76 to operate to permit flow of oil from lines 74 to lines 68, thus causing all the plug valves to open. After the high pressure is relieved below 19 pounds per square inch the contacts of control 126 will open and coils 130 and 132 are deenergized so that the controls 50 will be on automatic. Energization of coil 132 closes its contacts 132a completing a circuit through alarms 134 which may be either lights and/or audible horns. If any of the contacts 420 are closed when the pressure in the bustle pipe reaches 17.3 pounds per square inch a circuit will be completed through relay coil 112 causing its contacts 1120 to open so that no circuit will be completed through relay coil 110, thereby preventing speed control knob 104 from being adjusted to the fast position while allowing the system to remain on automatic.

When the air is cut off from the furnace, as when checking the furnace at the end of the cast, I have found that all of the plug valves 10 will eventually completely close due to the change in pressure balance on the controls 50. When the wind is put on the furnace again a terrific surge of pressure against the nearly closed plug valves endangers the blowing engines. The low pressure responsive switch 120 prevents closing of the plug valves under these conditions. When the pressure in the bustle pipe 5 drops be lows 13 pounds per square inch the contacts 120c of switch 120 will open. Since the contacts 1200 are in the neutral line of the directional circuit of motor 96, the motor 96 cannot operate to close the burden valve. When the pressure again rises above 13 pounds the contact 1200 will close and the controls 50 will again take over.

I have also found that the burden valve 92 may be connected to a separate clean air source having a constant pressure. This has the advantage that the dirt which is present in the air in the hot blast main will not interfere with the proper operation of the control. However, with this arrangement the burden motor 96 will operate more frequently.

While one embodiment of my invention has been shown and described it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of a tap line connected to said supply line, a burden valve in said tap line, a motor for operating said burden valve, an air flow determining means in said tap line on the exhaust side of said burden valve, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said last named air flow determining means to each of said regu: lators, control means for operating said burden valve motor to close said burden valve when a control valve opens beyond a predetermined amount, a second control means operable when all of the control valves close below a predetermined amount to open said burden valve, and means for causing said burden valve to open rapidly when the pressure in said supply line rises to a predetermined amount.

2. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of a tap line con nected to said supply line, a burden valve in said tap line, a motor for operating said burden valve, an air flow determining means in said tap line on the exhaust side of said burden valve, an automatic regulator associated with each tuyere for'controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said last named air flow determining means to each of said regulators, control means for operating said burden valve motor to close said burden valve when an obstruction occurs at a tuyere, a second control means operable when all of the control valves close belowa predetermined amount to open said burden valve, means for causing said burden valve to open rapidly when the pressure in said supply line rises to a predetermined amount, and means for talking said regulators off automatic and opening said control valves when the pressure in said supply line exceeds the last named pressure by a predetermined amount.

3. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of a tap line connected to said supply line, a burden valve in said tap line, a motor for operating said burden valve, an air flow determining means in said tap line on the exhaust side of said burden valve, an automatic regulator associated wtih each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting animpulse from said last named air flow determining means to each of saidregulators, control means for operating said burden valve motor to close said burden valve when an obstruction occurs at a tuyere, a second control means operable when all of the control valves close below a predetermined amount to open said burden valve, means for causing said burden valve to open rapidly when the pres sure in said supply line rises to a predetermined amount, means for taking said regulators ofi automatic and opening said control valves when the pressure in said supply line exceeds the last named pressure by a predetermined amount, and means for preventing operation of said burden valve motor when the pressure in said supply line falls below a predetermined amount.

4. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of a tap line connected to said supply line, a burden valve in said tap line, a motor for operating said burden valve, an air flow determining means in said tap line on the exhaust side of said burden valve, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said last named air flow determining means to each of said regulators, control means for operating said burden valve motor to close said burden valve when an obstruction occurs at a tuyere, a second control means operable when all of the control valves close below a predetermined amount to open said burden valve, and means for preventing operation of said burden valve motor when the pressure in said supply line falls below a predetermined amount.

5. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines, an air flow determining means associated with said supply line, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, and means connecting an impulse from said second named air flow determining means to each of said regulators; the combination therewith of control means operable when an obstruction occurs at a tuyere for causing the associated regulator to open the control valve of the obstructed tuyere and close the control valves of the remaining tuyeres, a second control means operable when all of the control valves close below a predetermined amount to open all of the control valves, and means for opening said control valves rapidly when the pressure in said supply line rises to a predetermined amount.

6. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, an air flow determining means in each of said pipe lines, an air flow determining means associated with said supply line, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, and means connecting an impulse from said second named air flow determining means to each of said regulators; the combination therewith of control means operable when an obstruction occurs at a tuyere for causing the associated regulator to open the control valve of the obstructed tuyere and close the control valves of the remaining tuyeres, a second control means operable when all of the control valves close below a predetermined amount to open all of the control valves, means for opening said control valves rapidly when the pressure in said supply line rises to a predetermined amount, and means for taking said regulators olf auto matic and opening said control valves when the pressure in said supply line exceeds the last named pressure by a predetermined amount.

7. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve ineach of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of means for developing a master signal, means for varying the magnitude of said master signal, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said master signal to each of said regulators, control means for operating said master signal varying means to decrease the magnitude of said master signal when any one of said control valves opens wider than a first predetermined amount, control means for operating said master signal varying means to increase the magnitude of said master signal when all said control valves close beyond a second predetermined amount, and means for increasing the magnitude of said master signal rapidly when the pressure in said supply line rises to a predetermined amount.

8. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of means for developing a master signal, means for varying the magnitude of said master signal, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said master signal to each of said regulators, control means for operating said master signal varying means to decrease the magnitude of said master signal when an obstruction occurs at a tuyere, a second control means operable when all of the control valves close below a predetermined amount to operate said master signal varying means to increase the magnitude of said master signal, means for increasing the magnitude of said master signal rapidly when the pressure in said supply line rises to a predetermined amount, and means for taking said regulators ofi automatic and opening said control valves when the pressure in said supply line exceeds'the last named pressure by a predetermined amount.

9. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of means for developing a master signal, means for varying the magnitude of said master signal, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said master signal to each of said regulators, control means for operating said master signal varying means to decrease the magnitude of said master signal when an obstruction occurs at a tuyere, a second control means operable when all of the control valves close below a predetermined amount to operate said master signal varying means to increase the magnitude of said master signal, means for increasing the magnitude of said master signal rapidly when the pressure in said supply line rises to a predetermined amount, means for taking said regulators oil automatic and opening said control valves when the pressure in said supply line exceeds the last named pressure by a predetermined amount, and means for preventing operation of said master signal varying means when the pressure in said supply line falls below a predetermined amount.

10. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valves in each of said pipelines, meals for varying the position of each con trol valve, and an air flow determining means in each of said pipe lines; the combination therewith of means for developing a master signal, means for varying the magnitude of said master signal, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said master signal to each of said regulators, control means for operating said master signal varying means to decrease the magnitude of said master signal when an obstruction occurs at a tuyere, a second control means operable when all of the control valves close below a predetermined amount to operate said master signal varying means to increase the magnitude of said master signal, and means for preventing operation of said master signal varying means when the pressure in said supply line falls below a predetermined amount.

11. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, an air flow determining means in each of said pipe lines, means for developing a master signal, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, and means connecting an impulse from said master signal to each of said regulators; the combination therewith of control means operable when an obstruction occurs at a tuyere for causing the associated regulator to open the control valve of the obstructed tuyere and close the control valves of the remaining tuyeres, a second control means operable when all of the control valves close below a predetermined amount to open all of the control valves, means for opening said control valves rapidly when the pressure in said supply line rises to a predetermined amount, and means for taking said regulators off automatic and opening said control valves when the pressure in said supply line exceeds the last named pressure by a predetermined amount.

12. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of means for developing a master signal, means for varying the magnitude of said master signal, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said master signal to each of said regulators, and means for automatically opening said control valves rapidly when the pressure in said supply line rises to a predetermined amount.

13. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of means for developing a master signal, means for varying the magnitude of said master signal, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said master signal to each of said regulators, means for automatically opening said control valves rapidly when the pressure in said supply line rises to a predetermined amount, and means for automatically taking said regulators oif automatic and opening said control valves when the pressure in said supply line exceeds the last named pressure by a predetermined amount.

14. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of means for developing a master signal, means for varying the magnitude of said master signal, an automatic regulator associated with each tuyere [for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said master signal to each of said regulators, means for automatically opening said control valves rapidly when the pressure in said supply line rises to a predetermined amount, means for automatically taking said regulators oif automatic and opening said control valves when the pressure in said supply line exceeds the last named pressure by a predetermined amount, and means for automatically preventing operation of said master signal varying means when the pressure in said supply line falls below a predetermined amount.

15. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of means for developing a master signal, means for varying the magnitude of said master signal, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said master signal to each of said regulators, means for automatically opening said control valves rapidly when the pressure in said supply line rises to a predetermined amount, and means for automatically preventing operation of said master signal varying means when the pressure in said supply line falls below a predetermined amount.

16. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of means for developing a master signal, means for varying the magnitude of said master signal, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said master signal to each of said regulators, and means for automatically taking said regulators off automatic and opening said control valves when the pressure in said supply line rises to a predetermined amount.

17. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of means for developing a master signal, means for varying the magnitude of said master signal, an automatic regulator associated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said master signal to each of said regulators, means for automatically taking said regulators ofi automatic and opening said control valves when the pressure in said supply line rises to a predetermined amount, and means for automatically preventing operation of said master signal varying means when the pressure in said supply line falls below a predetermined amount.

18. In a blast furnace having a plurality of tuyeres, an air supply line, a pipe line leading from said air supply line to each tuyere, a control valve in each of said pipe lines, means for varying the position of each control valve, and an air flow determining means in each of said pipe lines; the combination therewith of means for developing a master signal, means for varying the magnitude of said master-signal, an automatic regulator asso-' ciated with each tuyere for controlling the position of its associated control valve, means connecting an impulse from each of said first named air flow determining means to its associated regulator, means connecting an impulse from said master signal to each of said regulators, and means for automatically preventing operation of said master signal varying means when the pressure in said supply line falls below a predetermined amount.

References Cited in the file of this patent UNITED STATES PATENTS Re. 20,473 Lewis et a1 Aug. 17, 1937 1,713,833 Kochendorfer May 21, 1929 2,083,046 Burke June 8, 1937 2,185,970 Ziebolz Ian. 2, 1940 2,406,075 Graves et al. Aug. 20, 1946 2,774,368 Jones Dec. 18, 1956 

